The UI definitely needs a lot of work on mobile and is definitely not my favorite aspect of the app, but pushing new elements to it in its current state maybe a bit harder to get going. The devs here are prioritizing a lot of the backend due to bugs and user experience problems, that the UI is taking a bit of a back seat for the time being. If you are interested in working on it, feel free to ping me, and I’ll try to guide you through what I know about it and can also kind of steer you in the direction that you’re able to go at this time with it.
If you check the Github Issue tracker for any bugs or features that are tagged as mobile and gsoc, those are up for grabs along with any open bugs that aren’t assigned yet; these have been fully approved for students to work on. I would definitely also recommend searching for any specific UI changes you’re looking for before posting a request on the forums here. The mods are cracking down on duplicate posts and I’m trying to help them keep discussions centralized as much as possible.
Definitely check this out too: GSoC 2020 live blog